Electron discharge device



Oct '22, 1946.

ELECTRON- DISCHARGE DEVICE 'Filed Jan. 6, 1942, 2 Sheets-Sheet 2 1 ATTORNEY v E. c. oK Ess Y 2,409,693

Patented Oct. 22, 1946 UNITED STATES PATENT OFFICE ELECTRON DISCHARGE DEVICE- Ernest Carl Okress, Montclair, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 6, 1942, Serial No. 425,715

17 Claims. 1 This invention relates to electron discharge devices generally, and to the generation and utilization of ultra high frequency currents, the invention having reference, more particularly, to novel high frequency radio apparatus including hollow-body resonators.

The type of electron discharge device with which the present invention may be classified, consists essentially of two hollow conducting cir- .cuit members or resonators within which fields,

comprising standing electromagnetic waves, are adapted to be set up by the passage of a stream of electrons througha restrictedpart thereof.

Electron streams, in velocity modulated tubes, are of relatively highimpedance andmatchreadily the resonators through which they pass. The high electron stream impedance is obtained by means of ahigh potential, but low stream current. This procedure in the microwave region of a few centimeters wavelength encounters diniculties by seriously limiting the output of the oscillators, etc. to almost uselesslevels. Sincepractically there is a definite limit to the stream electron density the only other factor in increasing. current is to increase the cross section area of the stream. However, in the prior art, as related to the short microwave region, the resonators are scaled down to such an extent that the orifice area through which the'stream passes is much restricted. This reduces the stream current.

The effective Q of such a small resonator is appreciably influenced by the extent of the orifice; Hence, the ratio of orifice to resonator surface must be kept as small as possible andthisis not possible with conventional methods of enveloping the resonators around electron streams'without serious loss in electron stream current and hence output.

An object of the present invention is accordingly to improve upon prior art structures to overcome eifectively the deficiencies therein and:

justment and: support. by means having no; part:

Cir

crossing the said annular passageway to interfere with electron fiow except for the provision of resonator grids, whenever such be necessary.

A still further object of the present invention lies in the provision of novel forms of internally resonant hollow-body resonator members and. in combination with novel forms of cathode,

buncher, catcherand collector arrangedito react with the electron stream for useful and effective purposes.

Further objects of the invention include pro.- vision of a structure adaptable tobetter cooling,

simplicity of fabrication, stability of operation;

and other advantages and results which will appear to those skilled in the art, both by direct statement thereof and by implication from. the context.

In the accompanying drawings, wherein likenumerals of reference indicate similar parts throughout the several views, and wherein preierredphysical embodiments of the invention are disclosed by way of example;

Figure 1 is a longitudinal sectional view of" an electron discharge device or high frequency oscillator of the character'indicated and: forming the primary embodiment of the invention;

Figures 2 and-3 are cross-sectional views thereof on lines I[1I and III-III', respectively, of Fig. 1.

Figure 4 is a longitudinal sectional View similar to Fig. 1, showing the device constructed and connected to function as an auxiliary wave mixerfor obtaining a beat output; and

Figure 5 is an elevation of thedevice shown-in Fig. 4 but with: indication of connection for useas an amplifier.

In the specific embodiment-of the invention illustrated in said drawings, and with attention directed initially to Figures 1 to 3,. inclusive, the

reference numeral I0 designates an evacuated housing or envelope, the major portion whereof may be considered as comprising in general three. parts, namely; one end portion I l constituting a. chamber for the cathode, a second or adjoining portion 52 within which is situated a pair of resonator chambers l3; l4, field-free space l5 and grids [6; H, I8 and I9; and finally a third portion 20 constituting a collector chamber and housing a collector 2|.

Heretofore it has been the general practice in' connection with short-wave apparatus of this general type, to provide a cathode which produces a concentrated pencil-like beam of electrons to pass through constricted openings centrally through resonators and'to be. received by a collector of fiat disk conical shape. Such construction imposes limitations on input and output due to physical considerations. According to the present invention, however, the electron stream is made to surround the resonators and affects the alternating electric field thereof by constricted peripheral openings communicating with the surrounding electron stream. In general, my improved device provides a construction wherein the cathode 22 is of substantially concaved ring formation and accordingly produces with the aid of the cylindrical concave electrical mirror 22' a beam or stream of electrons which assumes the form of a hollow tube, this stream being directed through grids of flat ring shape and through a field-free space which is tubular in configuration, finally arriving at the collector which is preferably of hollow cylindrical formation with an end wall hollowed and directed to ward the electron stream so as to receive the electrons within an annular cavity 23, the cross section of which may preferably be V-shaped.

Furthermore, and generally speaking, the prior art has provided grids of relatively small diameter and large resonator chambers which have been annular in formation extending around the grids, said grids having been foraminous disks in central openings of the resonators. According to the present invention, the grids have a larger diameter than the resonators, which are likewise substantially within the confines of the portion of the device constituting the tube-like field-free space, and which accordingly have an outside diameter no greater than the inner diameter of the grids. The construction thus obtained,

provides a very considerable cathode area with attendant copious flow Of-electrons, and at the same time permits the utilization of the small resonators operating at the fundamental microwave frequencies of a few centimeters wavelength.

The field-free space i5 is formed as an annular passage, between two concentric cylindrical walls, of which the outer one is also the envelope wall for the mid-portion i2 thereof, whereas the inner cylindrical wall 24 of the field-free space is also the outer cylindrical walls of the resonators l3, M, of which more detail description will follow shortly. Sufiice it to say for the moment, that the inner cylindrical wall 24 is shorter than the outer cylindrical wall an amount sufficient to obtain a proper peripheral constricted openin 25 at each end thereof for the corresponding resonator, and proper spacing of the grids thereat. As shown, the first grid i6 is in a plane at the near end of the outer wall, that is to say, the end nearest to the cathode, and the second grid [1 is substantially parallel thereto at the near end of the inner wall 24 with a spacing between the grids and with the constricted opening 25 communicating therebetween, to impress a modifying influence upon the electron stream passing through those grids in consequence of the resonance of the first resonator chamber I3. Similarly, the second pair of grids l 8 and I9 are situated in parallelism to each other and to the first two grids and preferably separated substantially the same distance as the first two grids, the grid l8 nearest the cathode of the second pair being shown in the end plane at the far end of inner cylinder 24 and the second grid N of this pair is situated at the far end of the outer wall of the intermediate housing portion I2. The construction accordingly also provides a constriction or gap 25 existent between the inner peripheries of the grids l8, i9

'4 and opening into the second resonator chamber M The resonators, as indicated above, are included within the hollow of inner cylindrical wall 2 3 which accordingly forms the outer peripheral wall for each resonator. A transverse partition 26 midway of the length of said cylindrical wall 24 constitutes a common wall to both resonators, said partition being situated midway of the length of the cylindrical wall so the resonators will be of equal size. End walls 27, 28 are provided parallel to and equally spaced from and at opposite sides of the partition thereby defining the length of said resonators in an axial direction. These end walls have an outer diameter substantially equal to the diameter of the cylindrical wall 24, and have their peripheries opposite the ends of said cylindrical wall with appropriate spacing therefrom to thereby provide the peripheral constricted openings 25 above mentioned, one in each resonator. The nd wall Zl' of resonator 13 next the cathode end of the device has its outer periphery secured to the inner periphery of the first grid l6, and similarly, the far end wall 28 of the second resonator has its outer periphery secured to the inner periphery of the last grid 19 of the series of grids. The resonators are further defined by an inner cylindrical wall concentric with the Wall heretofore described as cylindrical. This said inner cylindrical wall is constituted, for the second resonator, by a portion of a tubulaar coaxial conductor, the tube part 29 of which extends inwardly of said resonator from the far end thereof through end wall 28 as far as partition 26. An extension 38 of this tubular wall is situated in the first resonator from said partition 25 to the forward end wall 21 forming a support for said end wall. Accordingly, in cross section, the first resonator is defined by cylindrical and concentric walls 24 and 3E! and by end wall 2'! and partition 26, whereas the second resonator is defined by cylindrical and concentric walls 24 and 29, partition 26 and end wall 28, the areas thus defined being substantially equal to each other. By proportioning the resonator chamber M with respect to its grid spacing and with respect to the resonator chamber 13 and grid spacing of grid l6, H, the resonance of these two resonator chambers may be made identical. The partition or disk-shaped wall 26 which separates the two chambers l3, M is provided with an appropriate Opening 3! and feed-back 32 therethrough as will be understood by those skilled in the art as a means for obtaining oscillation in the first resonator chamber l3 by oscillations produced in the second resonator chamber 54.

The tubular conduit or chamber i5 surrounding the resonators peripherally, constitutes the fieldfree space for travel of electrons and the length of this field-free space is proportioned with re spect to the wavelength with which the particular device is concerned. It will be understood that electrons emitted from the cathode arrive at the first grid I 6 and due to the resonance of chamber [3 the passage of electrons between the first grid [6 and the second grid I! is modified such that some electrons pass through unaffected as to velocity and other electrons are minutely slowed down whereas other electrons are minutely speeded up. The magnitude of the modulation is partially dependent upon the field strength between the grids l6, I! of the resonator 3. The electrons then pass through the field-free space :5 with the electrons having normal or unaffected speed overtaking previously dispatched somewhat slower electrons and in turn being overtaken by somewhat speeded-up electrons which started at a later moment. The proportional length of the field-free space is such that the proper concentration of electrons thus effected takes place between grids l8 and H3 at the far end of the fieldfree space. The electrons accordingly represent a concentration of energy and are capable of giving up energy to the second resonator when acted on by oscillating electric fields between grids I8, I 9 of the resonator M in the proper phase in accordance with classical theory. A small amount of this energy is utilized, as indicated above, as feed-back through loop 32 to the first resonator in order to modifyv the flow of other electrons between initial grids I6, I! that the cycle of operations above explained may continue.

The majority of the energy derived by the second resonator is carried on through a suitable output. As here shown the coupling means to the output comprises a coaxial line heretofore briefly mentioned and formed by a tube 29 extending from within the second resonator, through the collector and finally to the exterior of housing 10. Within the coaxial-line tube 29 is a central conductor 33 having a loop 34 at its outer end connected to the wall of tube 29 and having a loop 35 next its inner end which pro- J'ects into the resonator by means of an orifice 36 and is secured to a wall thereof, as for instance to partition 25. The outer end of tube 29 is suitably sealed, as by an electromagnetically transparent cap 31, and as the tube is likewise sealed to the housing It] where protruding therefrom, the interior of said tube and housing are maintained at the same vacuum. Loop 34 in the outer sealed end of tube 29 forms a coupling means to a suitable output circuit or apparatus indicated generally by tank or rectangular wave guide G.

The collector 2| is suitably supported by one or more spoke-like rods 38 radiating therefrom and one or all constituting lead-in connections as well as supports. Said rods are shown passing through electrically insulating collars 39 which have thimbles 40 sealed therein, said rods being soldered or otherwise secured to said thimbles. For lead-in purposes the said rods may be continued through the thimbles, in which event the rod and thimble must be secured with a vacuumtight seal. As indicated in Figure 3 there are three mountings provided for the collector, one of said mountings being shown in detail in Figure 1. It maybe furthernoted that the inner end of the insulating collar 39 above mentioned is secured with a vacuum seal in the outer end of a nipple 4| protruding from the peripheral wall of the collector housing portion 20. Within this nipple is situated a cup 42 concentric upon the rod with the closed end of the cup outwardly and with the side walls ofthe cup parallel to and spaced from the nipple 4!. This construction is helpful decreasing microwave energy passage to the exterior by means of the lead 38.

The rear part of electrical mirror 22' is an annulus and support therefor is obtained in a manner similar to that described with respect to the support for the collector and the parts constituting such support and lead-in connection are designated by the same reference numerals to which a prime mark has been added.

The cathode 22 is preferably indirectly heated by use of a coiled spring-like filament 43 which has a central disposition immediately behind the annular emitting surface of the cathode. The

lead-ins for the filament connect at diametrically opposite parts thereof so that the heating current divides and passes from one lead to the other through both halves of the filament. The lead-ins for the filament have the same structural elements as heretofore described with respect to the lead-ins and supports for the collector and are attached to and support the oathode. Accordingly the same reference numerals are applied thereto and distinguished by utilization of double prime marks thereon.

In order that the resonator chambers may be confined at their ends and tuned with respect to each other, the opposite end walls 21, 28 are shown flexible, being of resilient metal, and fixed only at their middle parts, with means provided for flexing the peripheral parts thereof.

Flexing of the first disk-like end Wall 2'! is preferably by means of a pressure foot 44 arranged with a peripheral engagement against the near face of said flexible end wall in the area thereof inward from the periphery. Suitable means is provided for applying pressure to this pressure foot 44 normal to and for purposes of flexing the wall inwardly and reducing the gap or constricted opening 25 between the same and the cylindrical wall 24, which accomplishes the desired tuning. A stop 45 is preferably situated at the middle or fixed part of the end wall 21 for engagement by the pressure foot to limit possible movement of said pressure foot. This construction will accordingly prevent undue depression of the pressure foot and undue flexing of the end wall and its attached grid, especially during evacuation of the envelope. The pressure means shown is constituted by a post-like structure 46 extending centrally from the pressure foot 44 through the hollow central portion of the cathode to a flexible outer envelope Wall 4'! the periphery of which is suitably vacuum sealed with respect to housing II]. A header 48 overlies the flexible wall and receives the threaded shank of a thumbscrew 49, said shank being directly opposed to post 46 and therefore capable of moving the post longitudinally inward as the thumbscrew is fed in that direction.

Because of the presence of the coaxial-line connector tube protruding from the far end of the envelope, it is not feasible to operate a pressure foot against the disk-like end Wall 28 of the second resonator l4 precisely as described above. Flexing may accordingly be obtained by other appropriate means. As shown, a pressure foot comprising a ring 56 is attached, by solder or otherwise, on the far side of the said disk-like end wall 23 near the periphery thereof, and from said ring project a plurality of posts 5| parallel to the axis of the envelope and normal to said.

ring and wall. These posts are each sealed through a flexible bellows-like Wall portion 52 inv the far end wall of the envelope. Flanges 53- on said posts next said end wall of the envelope engageable against underlying detents or fingers 54 prevent excessive flexing of the resonator end wall and its attached grid. The outer protruding ends of the several posts 5| are in engagement with the near face of an adjusting nut 55 screw threaded at 56 upon an outer threaded hub sun. rounding and fixed to the coaxialline tube 29 next the end wall of the envelope. The outer periphery of this nut 55 is knurled that it may be turned by hand for adjusting or other purposes.

The construction shown and thus far described accordingly provides an oscillator for micro-wave oscillations wherein the resonators are reduced to as small a diameter as desired and yet provides a cathode of considerable size and capable of producing a very considerable energy input, and at the same time enables the resonators to be tuned with precision, the precise tuning assuming greater importance as the Wave length employed comes within the range of micro-short-waves.

The features described above in their general aspects of resonators entirely within the confines of the volume defined by the tubular stream of electrons and with the resonators adjustable for tuning purposes, can be incorporated in other short Wave apparatus and oscillators, for instance, may be incorporated in auxiliary mixers and amplifiers as disclosed respectively in Figures 4 and 5. So far as they apply, therefore, like numerals of reference are carried over from the preceding description and additional numerals are used. on both of these figures where parts are the same, and with addition of prime and double prime marks in some instances.

The basic principle and a further embodiment of the invention depicted in Figure 4 as an auxiliary mixer will be described. For use of the device as an auxiliary mixer, it is desirable to duplicate the centrally disposed coaxial-line through the end portion of the envelope constituting the cathode chamber, and to omit the feed-back between the resonating chambers.

In Figure 4, the reference numeral 51 desi nates an evacuated housing or envelope, the major portion whereof may be considered as comprising in general three parts, namely, one end portion 58 constituting a chamberfor the oathode, a second or adjoining portion 59 within which is situated a pair of resonator chambers 6!), 6i, field-free space [5 and grids l6, ll, [8 and I9, and finally a third portion 62 constituting a collector chamber and housing a collector 63. Within the first portion 58 is situated an annular cathode 22 activated by a heater 43 behind the same, the lead-ins for which are shown at 38" protruding from the portion 58 in diametrically opposite parts thereof and sealed in the same manner as described in connection with Figure 1. The cathode is provided with an electrical mirror 22, and the grids and collector are of an annular formation situated in opposition to the annular cathode in the same manner as described with respect to Figure 1. In the present showing grid it next the cathode chamber and final grid l9 next the collector chamber are each secured at their inner peripheries to disk-like end-walls 64 of the respective resonators, which said endwalls are adjustable by flexing at their peripheries. Such flexing is for purposes of varying the constricted openings 25, respectively, between those disks and the outer peripheral walls 24 of the resonator chambers. It may be here noted that the resonator chambers 60, Bl are divided from each other by a disk-like partition 26' the periphery of which is secured to the peripheral wall 24 to situate said partition midway between the ends of said peripheral wall.

Centrally of the housing or envelope '5'! is provided a coaxial-line connection of which one tube part 29 extends through the far end of the envelope as described in connection with Fig. 1, and another aligned tube part 29' which extends oppositely outward from said partition 26' and projects from the near end of the device, necessarily, therefore, passing centrally through the cathode chamber, Both end parts of this coaxial-line tube are vacuum-sealed as by means of electromagnetically transparent caps 31, 31' of glass or other suitable material. Within said tube parts 29, 29' and coaxial therewith are alined rods or central conductors 33, 33, the outer ends of which are provided with loops 34, 34 within said caps 31, 37', the far ends of said loops attaching to the metallic portion of the tube. At the end of the tube part 29' which passes through the cathode chamber, said loop and cap project into a suitable wave guide or other source of oscillating energy which may be derived from an antenna. The opposite end of the tube part 29 which protrudes from the collector chamber is situated within another wave guide which, in turn, may receive its oscillations from any suitable oscillator. The energies thus received at opposite ends of the tube will be propelled as waves characterized by the frequency of the particular source from which derived. By virtue of loops 35, 35 in the resonators 60, 6| connected with the said rods 33, 33, respectively, the energy is introduced into the respective resonators and obtains corresponding oscillation therein. The result Will be impressed on the collector 63 as a beat output, which, for that purpose is shown with its face toward the cathode flat and parallel thereto,

The resonator end walls 64 are adjustable by fiexure at their peripheral margins, and substantially duplicate mean may be provided for obtaining adjustment of each. The means selected for the present showing for adjusting said end walls of the resonators and constricted openings, is essentially the same as heretofore described with respect to Fig. 1, at the collector end thereof, which description is believed sufiicient for this present showing and like numerals of reference are accordingly applied in Fig. 4 to the adjusting means at both ends of the device.

If it is desired to use the device as an amplifier, the internal construction above described with respect to Figures 1 to 4 may be utilized with appropriate selection of parts. Thus, a feed-back 55 is provided through partition 86 between resonators B7 and G8. The output is obtained at the end of the concentric-line tube 29 through an appropriate wave guide associated therewith; Collector 2! may be in duplication of the showing thereof in Fig. l.

I claim:

1. An electron discharge device comprising hollow-body resonators, an envelope having a conductive part providing a field-free space enclosed thereby and said field free space surrounding said resonators peripherally, said resonators having constricted openings at ends of said fieldfree space, a cathode in said envelope opposite an end of said field-free space for directing an electron stream through said field-free space, and a collector opposed to the cathode at the other end of, said field-free space.

2. An electron discharge device comprising resonators situated end to end and having peripheral constricted openings next the most distant ends thereof, an envelope having a conductive part providing a field-free space at the peripheral outside of the resonators extending the full length of said resonators from one said constricted opening to the other, and a cathode in said envelope opposed to one end of said fieldfree space, said cathode being annular and relatively large in comparison to the said resonators both as to diameter and area.

3. An electron discharge device comprising a conductive envelope having axially alined opposite end chambers and an intermediate portion, an annular cathode in one end chamber substantially in a plane transverse to the axis of said envelope, an annular collector similarly disposed in the oppositeend chamber and alined with said cathode, and a cylindrical wall within said intermediate portion of the envelope dividing said portion into resonator space within the confines of said cylindrical walland into a field-free space for the entire part of said portion between the envelope wall and said cylindrical wall, said. fieldfree space thereby being tubular and being alined with and between the cathode and collector.

4. An electron discharge device comprising a conductive envelope having axially alined opposite end chambers and an intermediate portion, an annular cathode in one end chamber substantially in a plane transverse to the axis of said envelope, an annular collector similarly disposed in the opposite end chamber and alined with said cathode, and a cylindrical wall within said intermediate portionof the envelope dividing said portion into resonator space within the confines of said cylindrical wall and into a field-free space for the entire part of said portion between the envelope wall and said cylindrical wall, said fieldfree space thereby being tubular and being alined with and between the cathode and collector and said cylindrical Wall being shorter than and symmetrically disposed with respect to the said resonator space for providing constricted peripheral openings at the distant ends of the said resonator space into the ends of the field-free space, and means for varying the said constricted openings for tuning purposes.

5. An electron discharge device comprising hollow-body resonators, an envelope having a conductive part providing a field-free space enclosed thereby and said field-free space surrounding said resonators peripherally, said resonators having constricted openings at ends of said fieldfree space, a cathode in said envelope opposite an end of said field-free space for directing an electron stream through said field-free space, a

collector opposed to the cathode at the other end of said field-free space, and a coaxial-line coupling connection centrally disposed with respect to the resonators and having a loop in one of said resonators.

6. An electron discharge device comprising hollow-body resonators, an envelope having a conductive part providing a field-free space enclosed thereby and said field-free space surrounding said resonators peripherally, said resonators having constricted openings at ends of said fieldfree space, grids at opposite ends of said fieldfree space and at end walls of said resonators, said grids being in pairs at oppositev sides of said constrictedopenings, a cathode in said envelope opposite an end of said field-free space for directing a stream of electrons to "and through said grids and field-free space, and a collector beyond and opposed to the last of the series of grids for receiving electrons passing through said grids.

7. An electron discharge device comprising hollow-body resonators, an envelope having a conductive part providing a, field-free space enclosed therebyand said field-free space surrounding said resonators peripherally, said resonators having constricted openings at ends of said fieldfree space, grids at opposite ends of said fieldfree space and at end walls of said resonators, said grids being in pairs at opposite sides of said constricted openings, a cathode in said envelope opposite an end of said field-free space for directing a stream of electrons to and through said grids and field-free space, a collector beyond and l0 opposed to the last of the series of grids for receiving electrons passing through said grids, and a coaxial-line coupling connection centrally disposed with respect to the resonators and having a loop in one of said resonators.

*8. An electron discharge device comprising hollow-body resonators, an envelope having a conductive part providing a field-free space en- "closed thereby and-said field-free space surrounding said resonators peripherally, said resonators havingconstricted openings at ends or" said fieldi'ree space, grids at opposite ends of said fieldiree space and at *end walls of said resonators, the mid-portion of "one of said end walls being fixed and the peripheral margin of said one end wall being flexible, said grids being in pairs at opposite sides of said constricted openings, means for flexing said margin of said one resonator end wall and grid for varying the constriction of said constricted opening, a cathode in said envelope 7 oppositean end of said field-free space for directing a stream of electrons to and through said grids and field-free space, and a collector beyond and opposed to the last of the series of grids for receiving electrons passing through said grids.

9. An electron discharge device comprising hollow-body resonators, an envelope having a conductive part providing an annular field-free space enclosed thereby and said field free space surrounding said resonators peripherally, said resonators having constricted openings at ends of said field-free space, annular grids at opposite ends of said field-free space and at end walls of said resonators, said grids being in pairs at opposite sides of said constricted openings, an annular cathode in said envelope opposite an end of said field-free space for directing a hollow cylindrical stream of electrons to and through said grids and field-free space, an annular collector beyond and opposed to the last'of the series of grids for receiving electrons passing through said grids, and a coaxial-line coupling connection centrally disposed with respect to the resonators and having a loop in one of said resonators.

10. An electron discharge device comprising cylindrical hollow-body resonators, a cylindrical envelope coaxial therewith and having a conductive part providing an annular field-free space enclosed thereby and said field-free space surrounding said resonators peripherally, said resonators having constricted openings at ends of said field-free space, a cathode in said envelope opposite an end of said field-free space for directing an-electron stream through said field-free space, a collector opposed to the cathode at the other end of saidfield-free space, means concentrio with said envelope and projecting from one end thereof for wave propagation with respect to one resonator, and means projecting at opposite end of the envelope concentric therewith for tuning the other resonator with respect to said one resonator.

11. An electron discharge device comprising cylindrical hollow-body resonators, a cylindrical envelope coaxial "therewith and having a conductive part providing an annular field-free space enclosed thereby and said field free space surrounding said resonators peripherally, said resonators having constricted openings at ends of said field-free space, a cathode in said envelope opposite an end of said field-free space for directing an electron stream through said field-free space, a collector opposed to the cathode at the other end of said field-free space, a coaxial-line coupling connection centrally disposed with respect to the resonators and having a loop in one of said resonators, a flexible Wall at the opposite end of said envelope from said coupling connection, means extending from said flexible wall to the end of the nearest resonator for tuning that resonator by flexing said wall, and means for flexing said wall.

12. An electron discharge device comprising hollow-body resonators, an envelope having a conductive part providing a field-free space enclosed thereby and said field free space surrounding said resonators peripherally, said resonators having constricted openings at ends of said fieldfree space, grids at opposite ends of said fieldfree space and at end walls of said resonators, said grids being in pairs at opposite sides of said constricted openings, a cathode in said envelope opposite an end of said field-free space for directing a stream of electrons to and through said grids and field-free space, a collector beyond and opposed to the last of the series of grids for receiving electrons passing through said grids, and externally operable means extending to one of the end walls of the resonator for moving said wall next a constricted opening and thereby tuning the resonator.

13. An electron discharge device comprising hollow-body resonators, an envelope having a conductive part providing a field-free space enclosed thereby and said field free space surrounding said resonators peripherally, said resonators having constricted openings at ends of said field-free space, grids at opposite ends of said field-free space and at end walls of said resonators, said grids being in pairs at opposite sides of said constricted openings, means for flexing one resonator end Wall and grid for varying the,

constriction of said constricted opening, said means comprising a flexible end wall for the envelope connected to a peripheral part of the end wall of the resonator by which flexing of the end wall of the envelope obtains corresponding flexing of the end wall of the resonator, a cathode in said envelope opposite an end of said field-free space for directinga stream of electrons to and through said grids and field-free space, and a collector beyond and opposed to the last of the series of grids for receiving electrons passing through said grids.

14. An electron discharge device comprising hollow-body resonators, an envelope having a conductive part providing an annular field-free space enclosed thereby and said field-free space surrounding said resonators peripherally, said resonators having constricted openings at ends of said field-free space, annular grids at opposite ends of said field-free space and at end walls of said resonators, said grids being in pairs at opposite sides of said constricted openings, an annular cathode in said envelope opposite an end of said field-free space for directing a hollow cylindrical stream of electrons to and through said grids and field-free space, an annular collector beyond and opposed to the last of the series of grids for receiving electrons passing through said grids, a pressure foot having an edge thereof in contact with a marginal part of one end'wall of one resonator adjacent an annular grid, and means for operating said pressure foot transverse to said end wall of the resonator and thereby altering the constriction of the constricted opening for tuning purposes.

15. An electron discharge device comprising hollow-body resonators, an envelope having a conductive part providing a field-free space enclosed thereby and said field-free space surrounding said resonators peripherally, said resonators having constricted openings at ends of said fieldfree space, grids at opposite ends of said fieldfree space and at end walls of said resonators, said grids being in pairs at opposite sides of said constricted openings, means for flexing one resonator end wall and grid for varying the constriction of said constricted opening, said means comprising pressure foot engaging said resonator end wall and having a plurality of posts projecting therefrom and through the end wall of the envelope, bellows-like means in the end wall of the envelope permitting movement of said posts and the end wall of the resonator, a cathode in said envelope opposite an end of said field-free space for directing a stream of electrons to and through said grids and field-free space, and a collector having a flat face opposed to the last of the series of grids for receiving electrons passing through said grids.

16. An electron discharge device comprising hollow-body resonators, an envelope having a conductive part providing a field-free space enclosed thereby and said field-free space surrounding said resonators peripherally, said resonators having constricted openings at ends of said fieldfree space, grids at opposite ends of said fieldfree space and at end walls of said resonators, said grids being in pairs at opposite sides of said constricted openings, means for flexing one resonator end wall and grid for varying the constriction of said constricted opening, said means comprising pressure foot engaging said resonator end wall and having a plurality of posts projecting therefrom and through the end Wall of the envelope, bellows-like means in the end wall of the envelope permitting movement of said posts and the end wall of the resonator, a cathode in said envelope opposite an end of said field-free space for directing a stream of electrons to and through said grids and field-free space, and a collector having a recessed face opposed to the last of the series of grids for receiving electrons passing through said grids.

17. An electron discharge device comprising hollow-body resonators, an envelope having a conductive part providing a field-free space enclosed thereby and said field-free space surround ing said resonators peripherally, said resonators having constricted openings at ends of said fieldfree space, grids at opposite ends of said fieldfree space and at end walls of said resonators, said grids being in pairs at opposite sides of said constricted openings, a cathode in said envelope opposite an end of said field-free space for directing a stream of electrons to and through said grids and field-free space, a collector beyond and opposed to the last of the series of grids for receiving electrons passing through said grids, a coaxial-line coupling connection centrally disposed with respect to the resonators and having a onator.

ERNEST C. OKRESS. 

